explain_mount man page

explain_mount — explain mount(2) errors

Synopsis

#include <libexplain/mount.h>

const char *explain_mount(const char *source, const char *target, const char *file_systems_type, unsigned long flags, const void *data);
const char *explain_errno_mount(int errnum, const char *source, const char *target, const char *file_systems_type, unsigned long flags, const void *data);
void explain_message_mount(char *message, int message_size, const char *source, const char *target, const char *file_systems_type, unsigned long flags, const void *data);
void explain_message_errno_mount(char *message, int message_size, int errnum, const char *source, const char *target, const char *file_systems_type, unsigned long flags, const void *data);

Description

These functions may be used to obtain explanations for errors returned by the mount(2) system call.

explain_mount

const char *explain_mount(const char *source, const char *target, const char *file_systems_type, unsigned long flags, const void *data);

The explain_mount function is used to obtain an explanation of an error returned by the mount(2) system call. The least the message will contain is the value of strerror(errno), but usually it will do much better, and indicate the underlying cause in more detail.

The errno global variable will be used to obtain the error value to be decoded.

source
The original source, exactly as passed to the mount(2) system call.
target
The original target, exactly as passed to the mount(2) system call.
file_systems_type
The original file_systems_type, exactly as passed to the mount(2) system call.
flags
The original flags, exactly as passed to the mount(2) system call.
data
The original data, exactly as passed to the mount(2) system call.
Returns:
The message explaining the error. This message buffer is shared by all libexplain functions which do not supply a buffer in their argument list. This will be overwritten by the next call to any libexplain function which shares this buffer, including other threads.

Note: This function is not thread safe, because it shares a return buffer across all threads, and many other functions in this library.

Example: This function is intended to be used in a fashion similar to the following example:

if (mount(source, target, file_systems_type, flags, data) < 0)

{

fprintf(stderr, "%s\n", explain_mount(source, target, file_systems_type, flags, data));

    exit(EXIT_FAILURE);
}

The above code example is available pre-packaged as the explain_mount_or_die(3) function.

explain_errno_mount

const char *explain_errno_mount(int errnum, const char *source, const char *target, const char *file_systems_type, unsigned long flags, const void *data);

The explain_errno_mount function is used to obtain an explanation of an error returned by the mount(2) system call. The least the message will contain is the value of strerror(errno), but usually it will do much better, and indicate the underlying cause in more detail.

errnum
The error value to be decoded, usually obtained from the errno global variable just before this function is called. This is necessary if you need to call any code between the system call to be explained and this function, because many libc functions will alter the value of errno.
source
The original source, exactly as passed to the mount(2) system call.
target
The original target, exactly as passed to the mount(2) system call.
file_systems_type
The original file_systems_type, exactly as passed to the mount(2) system call.
flags
The original flags, exactly as passed to the mount(2) system call.
data
The original data, exactly as passed to the mount(2) system call.
Returns:
The message explaining the error. This message buffer is shared by all libexplain functions which do not supply a buffer in their argument list. This will be overwritten by the next call to any libexplain function which shares this buffer, including other threads.

Note: This function is not thread safe, because it shares a return buffer across all threads, and many other functions in this library.

Example: This function is intended to be used in a fashion similar to the following example:

if (mount(source, target, file_systems_type, flags, data) < 0)

{
    int err = errno;

fprintf(stderr, "%s\n", explain_errno_mount(err, source, target, file_systems_type, flags, data));

    exit(EXIT_FAILURE);
}

The above code example is available pre-packaged as the explain_mount_or_die(3) function.

explain_message_mount

void explain_message_mount(char *message, int message_size, const char *source, const char *target, const char *file_systems_type, unsigned long flags, const void *data);

The explain_message_mount function is used to obtain an explanation of an error returned by the mount(2) system call. The least the message will contain is the value of strerror(errno), but usually it will do much better, and indicate the underlying cause in more detail.

The errno global variable will be used to obtain the error value to be decoded.

message
The location in which to store the returned message. If a suitable message return buffer is supplied, this function is thread safe.
message_size
The size in bytes of the location in which to store the returned message.
source
The original source, exactly as passed to the mount(2) system call.
target
The original target, exactly as passed to the mount(2) system call.
file_systems_type
The original file_systems_type, exactly as passed to the mount(2) system call.
flags
The original flags, exactly as passed to the mount(2) system call.
data
The original data, exactly as passed to the mount(2) system call.

Example: This function is intended to be used in a fashion similar to the following example:

if (mount(source, target, file_systems_type, flags, data) < 0)

{
    char message[3000];

explain_message_mount(message, sizeof(message), source, target, file_systems_type, flags, data);

    fprintf(stderr, "%s\n", message);
    exit(EXIT_FAILURE);
}

The above code example is available pre-packaged as the explain_mount_or_die(3) function.

explain_message_errno_mount

void explain_message_errno_mount(char *message, int message_size, int errnum, const char *source, const char *target, const char *file_systems_type, unsigned long flags, const void *data);

The explain_message_errno_mount function is used to obtain an explanation of an error returned by the mount(2) system call. The least the message will contain is the value of strerror(errno), but usually it will do much better, and indicate the underlying cause in more detail.

message
The location in which to store the returned message. If a suitable message return buffer is supplied, this function is thread safe.
message_size
The size in bytes of the location in which to store the returned message.
errnum
The error value to be decoded, usually obtained from the errno global variable just before this function is called. This is necessary if you need to call any code between the system call to be explained and this function, because many libc functions will alter the value of errno.
source
The original source, exactly as passed to the mount(2) system call.
target
The original target, exactly as passed to the mount(2) system call.
file_systems_type
The original file_systems_type, exactly as passed to the mount(2) system call.
flags
The original flags, exactly as passed to the mount(2) system call.
data
The original data, exactly as passed to the mount(2) system call.

Example: This function is intended to be used in a fashion similar to the following example:

if (mount(source, target, file_systems_type, flags, data) < 0)

{
    int err = errno;
    char message[3000];

explain_message_errno_mount(message, sizeof(message), err, source, target, file_systems_type, flags, data);

    fprintf(stderr, "%s\n", message);
    exit(EXIT_FAILURE);
}

The above code example is available pre-packaged as the explain_mount_or_die(3) function.

See Also

mount(2)
mount file system
explain_mount_or_die(3)
mount file system and report errors

Referenced By

explain(3), explain_mount_or_die(3).